1. Field of the Invention
The present invention relates to a pressure sensor and an attaching mechanism for attaching the pressure sensor to an attaching member such as an internal combustion engine of a vehicle. For example, the pressure sensor according to the present invention is applicable to a combustion pressure sensor capable of detecting a combustion pressure of an internal combustion engine mounted on a vehicle. The pressure sensor according to the present invention is composed of a pressure sensing diaphragm, a pressure sensing chip, and a pressure transmission member, and capable of detecting a pressure received by the pressure sensing diaphragm and transferred from the pressure sensing diaphragm to the pressure sensing chip through the pressure transmission member.
2. Description of the Related Art
Related art techniques, for example, Japanese patent laid open publication No. JP H5-34231 has proposed and disclosed a pressure sensor composed of a pressure sensing diaphragm, a sensing unit such as a pressure sensing chip, and a pressure transmission member in which the pressure sensing diaphragm is placed in one end of a hollow cylindrical metal case, the pressure transmission member is placed in a hollow part of the hollow cylindrical metal case, and the pressure sensing chip is placed at the other end of the hollow cylindrical metal case. The pressure sensing diaphragm is deformed by receiving the pressure.
Such a type of the pressure sensor is applied to a combustion pressure sensor for vehicles. In a concrete example, the hollow cylindrical metal case is inserted into an attaching hole formed in an internal combustion engine of a vehicle, and fixed to the internal combustion engine. In this example, the internal combustion engine acts as an attaching member. The pressure sensing diaphragm receives a pressure (or a chamber pressure) of the internal combustion engine, namely, receives a combustion pressure in a combustion chamber of the internal combustion engine. The sensing unit such as a pressure sensing chip receives the signal of the received pressure transferred from the pressure sensing diaphragm through the pressure transmission member.
There is a possibility to expose the pressure sensing diaphragm and the pressure sensing chip, which are main components of the combustion pressure sensor, to a measuring atmosphere at a high temperature. Such a type of the related art pressure sensor having the configuration described above is attached to the attaching member by inserting and fixing the hollow cylindrical metal case into the attaching hole of the attaching member. Because the hollow cylindrical metal case is completely surrounded by the attaching hole, the thermal energy transmitted from the internal combustion engine can not be radiated. When the thermal energy is applied to the pressure sensing diaphragm under an actual measuring condition, there is a possibility of generating a strain in the pressure sensing diaphragm by receiving the thermal energy. The thermal energy increases the temperature of the pressure sensing unit such as the pressure sensing chip, so that the temperature of a pressure sensing unit exceeds its own operation allowable temperature. Finally, the pressure sensing chip falls to operation failure.
For example, in case of the combustion pressure sensor, highly thermal energy generated by a combustion chamber or cylinders is directly supplied to the pressure sensing diaphragm and the pressure sensing chip, the strain of the pressure sensing diaphragm and the operation failure of the pressure sensing chip easily caused. Such strain and operation failure causes detection errors of the pressure sensor. As a result, pressure sensor generates a large magnitude of detection error.